The present invention relates to coordinate measuring machines of the type having a movable probe for engaging an object. More particularly, the present invention has particular application to a coordinate measuring machine in which a probe movable in several independent directions is moved to inspect the object and may touch the object while the probe is still moving. The present invention also has application to height gages in which only a single direction is being measured.
In such machines, it is desirable to have an output readout system which identifies the precise location of contact between the probe (or a height gage's contact member) and the object. Such systems are well known in the prior art and in commercial use generally.
In such systems, it is also desirable, however, to also provide information on present location of the probe (or contact member) at all times. In the systems described in the preceeding paragraph, however, this information is not available, because the counter has stopped and only the position information regarding the present location of the probe is available.
Prior art systems could display the present location of the probe. However, in such systems, if the probe had been moving at the time of contact, the present location is not where the probe met the object. Consequently, with the systems of the prior art, one either had present probe location or a location of the contact point, but not both.
Future calculated locations of the probe are determined generally by the present location of the probe plus an increment of movement of the probe. Lack of present position information of the probe defeats such calculations and requires a rezeroing of the machine, that is, a movement of the probe to a predetermined reference point to again rezero the machine before proceeding with the measurement.
It is undesirable to rezero the machine after each measurement, but a system which retains and displays only the point of contact does require such information. Alternatively, the probe might be relocated to the point of contact, but, again, this is time consuming and troublesome, as well as a possible source of inaccuracies to perform the measurements.
Using a peripheral computer has been suggested to record the point of contact while the counter continues to record the present position. Such systems are expensive and require considerable programming to obtain accurate measurements.
Prior art systems for providing coordinate measurements are shown in U.S. Pat. Nos. 3,748,043; 3,740,532; 3,713,139; 3,691,353 and others.
Accordingly, the prior art systems of providing coordinate measurements have limitations and disadvantages which make them undesirable.